Imidized acrylic resins are known in the art; see for example, Graves U.S. Pat. No. 2,146,209 and Kopchik U.S. Pat. No. 4,246,374. These resins are prepared by reacting ammonia, or a primary amine with an acrylic polymer such as polymethyl methacrylate to form an imidized acrylic polymer (which are also called polyglutarimides). It is also known to combine imidized acrylic polymers with other materials, such as impact modifiers, pigments, fibers, stabilizers, lubricants etc., as described in said U.S. Pat. No. 4,246,374 at column 4, line 45 to column 5, line 58, and in U.S. Pat. No. 4,217,424 to Weese et al. It is also known to mix imidized acrylic polymers with vinyl chloride polymers and copolymers, as described in Kopchik U.S. Pat. No. 4,255,322 to improve heat distortion temperatures of the vinyl chloride polymers.
It is desirable to increase the stiffness, i.e., the flexural modulus of polyamide molding resins in order to obtain good resistance to cracking or breakage of polyamide molded articles that are subjected to flexing stress. Heretofore, stiffness of such polyamides has been increased by adding such material as glass fibers or mineral fillers. However, modification of properties of polyamides by adding imidized acrylic polymers has not heretofore been known.